Understanding of Regional Air Pollution over China using CMAQ: Model Evaluation and Process Analysis
The IPR analysis shows that vertical and horizontal transports are most influential factors for both O3 and PM10. They are the main sources of O3 at most sites and could either increase or deplete PM10 concentrations significantly. In addition to dry deposition, gas-phase chemistry is the dominate process for O3 destruction, particularly at urban sites. Cloud processes contribution to PM10 is not significant at most sites. Aerosol processes contribute more to the formation or destruction of NO3- and second organic aerosols. O3-NOx-VOC regime analysis suggests that NOx-limited atmosphere covers almost entire China in summer except several metropolitan areas such as Beijing, Shanghai, Tianjing, and several cities in the Pearl River Delta area where the VOC-limited condition dominates through entire year. The O3 chemistry over the North China Plain and northeastern China changes from NOx-limited condition to VOC-limited chemistry in winter. Apr and Oct are the transition periods when some areas over eastern China experience conversions between VOC-limited and NOx-limited condition.